Ribosomal RNA genes ofPhaseolus coccineus V. Relationship between rDNA phenotype and somatic differentiation

Summary Size variations in the intergenic spacer of ribosomal DNA were detected between individual plants of openly pollinatedPhaseolus coccineus. Eleven days after sowing, two plant samples were examined: slowly developing plants with a length less than 40 cm; and fast developing plants with a length greater than 70 cm. The two samples were characterized by different plant weight and, at maturity, by highly distinctive seed yield. They also exhibited distinct patterns of protein expression as analyzed by 2-D electrophoresis. In particular a 38 kDa protein, related to malate dehydrogenase on the basis of its N-terminal sequence, was present at higher concentration and higher activity levels in fast developing plants. Intergenic spacer length variants were detected in both samples at approximately 180 bp intervals. More than one spacer length variant was present in each individual plant. At least 13 different intergenic spacer hybridization patterns were in fact detected: some patterns occurred equally in both slowly and fast developing samples while the majority of patterns was significantly different between the two samples.Abbreviations FDP fast developing plants - IGS intergenic spacer - MDH malate dehydrogenase - rDNA SLV spacer length variant of ribosomal DNA - SDP slowly developing plants